1. Field of the Invention
This invention relates to an optical disc recording apparatus, an optical disc recording method, and an optical disc, and the present invention is applied to, for example, apparatus for recording on a compact disc, compact discs, and compact disc players. In the present invention, by locally changing the reflection film on a disc on which information has been recorded previously in the form of pit string, sub-data strings are recorded so that the main data string is reproducible by an optical pickup for reproducing the main data string and the main data string is difficult to be copied illegally without any adverse effect on reproduction of the main data string in the form of pit string.
2. Description of Related Art
Heretofore, in recording the data on a compact disc, a data string to be recorded is subjected to data processing, and then subjected to EFM modulation (Eight to Fourteen Modulation) to form pit string having a time period of 3T to 11T, T denotes a predetermined basic cycle, and the audio data or the like is recorded.
On the other hand, a management data recording area is formed on a lead-in area on the inside peripheral side, and a desired music or the like can be reproduced selectively with aid of TOC (Table Of Contents) recorded on the recording area.
On compact discs in which various data are recorded, codes which indicate the name of the maker and facility and disc number are marked on the inside of the lead-in area so that the history of a compact disc is recognized visually.
By recognizing the history of a compact disc with reference to such a mark, illegal copy is distinguished depending if there is a mark or not. However, such a mark is marked so as to be recognized visually, but the mark is not reproduced by an optical pickup of a compact disc player. Therefore, a reproduction mechanism which is exclusively used for reproduction of the mark is required separately to identify illegal copy based on the mark.
Because the code which has been recorded by these methods is recorded in the same manner as used for recording the normal pit, the code can be duplicated by a method in which the protective film and aluminum reflection film of a compact disc is separated and a stamper is made based on the separated films, and the data could be copied illegally.
It is considered that, if the sub-information is recorded so that the sub-information is reproducible by an optical pickup for reproducing the audio data and illegal copy is made difficult without any adverse effect on reproduction of the audio data in the form of pit string, illegal copy is prevented by use of the secondary information.
The present invention was accomplished in view of this problem, and provides an optical disc recording apparatus, an optical disc recording method, and an optical disc made by applying the optical disc recording apparatus or the optical disc recording method, in which the sub-information is recorded so that the sub-information is reproducible by an optical pickup for reproducing the data in the form of pit string and illegal copy is made difficult without any adverse effect on reproduction of the audio data in the form of pit string, illegal copy is prevented by use of the secondary information.
To solve the above-mentioned problem, the present invention provides an optical disc recording apparatus and an optical disc recording method in which the reflectance of the information recording surface is changed by changing the light quantity of a light beam irradiated onto a disc like recording medium on which the main data string is recorded in the form of repeated pits on the information recording surface to record the sub data string.
The sub-data string is recorded by changing the reflectance of the information recording surface on the pits and/or lands of the optical disc.
The sub-data recorded in the form of reflectance change of the information recording surface on the disc like recording medium on which the information has been recorded in the form of convex/concave such as pit is not copied by the copying method in which the reflection film is separated and a stamper is made. Thereby, the sub-data string is recorded so that the data of the optical compact disc is protected from being illegally copied. Further, only by minimizing the reflectance change caused from the sub-data recorded as described herein above, the adverse effect of the sub-data on reproduction of the main data is avoided. Further, the sub-data recorded in the form of reflectance change can be detected and decoded as the change of reproduction signal by an optical pickup.
Further, in the present invention, 1 bit sub-data is recorded over a plurality of pits and lands. The reflectance of the information recording surface can be changed locally at the position located a predetermined distance apart from the edge. In the case that the present invention is structured as described herein above, the reflectance can be significantly changed locally without any adverse effect on the timing of the edge. As the result, the sub-data string recorded in the form of significant reflectance change can be reproduced consistently.
Thus in the optical disc as described herein above, the main data string is recorded in the form of repeated pits having the length corresponding to the main data string on the information recording surface and the pit is recorded in the form of physical configurational change of the information recording surface, and the sub-data string is recorded in the form of reflectance change of the information surface, such structure described herein above protects the data in the optical disc from being copied.